Leaf Spring Foot Orthosis for Plantar Flexion Control
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Solution Overview
Problem
Foot drop, a condition characterized by impaired ability to dorsiflex the foot, leads to walking instability and increased risk of falling due to abnormal gait patterns and involuntary plantar flexion.
Innovation Solution
A leaf spring assembly is placed across the ankle joint, with one end attached to the shin and the other to the dorsal side of the foot, limiting plantar flexion to 10-15 degrees and maintaining the foot at a desired angle relative to the leg, thereby reducing foot drop and improving gait.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a leaf spring is placed across the ankle joint to limit plantar flexion, then foot drop is reduced and gait stability is improved, but the device increases structural complexity and may restrict natural ankle motion
Solution Approach 1:
The patent employs a leaf spring made of flexible material that can be conformably placed across the ankle joint. The spring's flexibility allows it to adapt to the joint's contours while providing the necessary mechanical constraint to limit plantar flexion and prevent foot drop, thereby improving gait stability without requiring complex rigid structures
Solution Approach 2:
The leaf spring acts as an intermediary mechanical element between the patient's impaired ankle joint and the desired gait correction. It mediates the motion by providing a controlled constraint that limits excessive plantar flexion while allowing other necessary movements, thus achieving gait stability without direct rigid fixation
2Manufacturing precision
If the leaf spring is constrained between the shin and foot to maintain foot position, then plantar flexion is limited to 10-15 degrees, but the middle portion of the spring does not contact the joint surface, forming a gap that reduces control
Solution Approach 1:
The leaf spring is designed to operate effectively even with a gap between its middle portion and the joint surface. The spring's elastic deformation in the dimension perpendicular to the joint surface provides sufficient control authority, demonstrating that contact in one dimension (ends anchored to shin and foot) can achieve precision control without continuous contact in another dimension (middle portion gap)
3Ease of operation
If the leaf spring assembly uses multiple layered leaves, then the device provides better flexibility and comfort, but the manufacturing complexity and assembly difficulty increase
Solution Approach 1:
The leaf spring is segmented into multiple layered leaves of decreasing length, with each leaf providing incremental flexibility. This segmentation allows the distal end to remain flexible for comfort and adaptability while the proximal end maintains sufficient rigidity for effective constraint, achieving both comfort and control without requiring complex multi-component assemblies
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of the leaf spring assembly effectively reduces foot drop by limiting excessive plantar flexion, thereby improving walking stability, reducing the risk of falls, and facilitating natural dorsiflexion.
Implementation Method 1
a leaf spring assembly... limiting plantar flexion to 10-15 degrees and maintaining the foot at a desired angle relative to the leg
Data Source
AI summary
Apparatus (20, 200) including a leaf spring assembly (22, 220) shaped to define a first end (32), a second end (34), and a middle portion (36) including a plurality of layered leaf springs (40). The spring is placed across a joint such that the first end is placed against a first location on a first side of the joint, and the second end is placed against a second location on a second side of the joint. When the leaf spring is constrained between the first and second locations, the middle portion (36) bridges a gap (120) formed between the middle portion and the joint. Additionally, a position of a first portion of a limb on the first side of the joint is maintained at a desired angle with respect to a second portion of the limb on the second side of the joint. Other embodiments are also described.